Mud pulse telemetry system

Abstract

A mud pulser tool to be positioned into a downhole environment is disclosed. The mud pulser tool includes a control valve that is selectively opened to allow fluid to flow through the mud pulser tool or selectively closed to restrict the fluid flow, wherein the control valve is selectively opened or closed to produce a mud pulse signal transmitted through the fluid. The mud pulser tool also includes a sensor system to measure a pressure drop across the control valve. In one example, the mud pulser tool includes a control system to selectively open or close the control valve to adjust the pressure drop to produce a selected pressure drop across the control valve.

What is claimed is: 
     
       1. A mud pulser tool to be positioned into a downhole environment, comprising:
 a housing; 
 a control valve positioned in said housing that is selectively opened to allow a fluid to flow through the mud pulser tool or selectively closed to restrict the fluid flow, wherein the control valve is selectively opened or closed to produce a mud pulse signal transmitted through the fluid, said control valve comprising;
 an orifice positioned in said housing; and 
 a poppet actuated linearly relative to said orifice, wherein a distance between said poppet and orifice is adjustable; 
 
 a sensor system to measure a pressure drop across the control valve; and 
 a control system coupled to said control valve, wherein said distance between said poppet and orifice is adjusted to achieve a desired differential pressure across said control valve, the mud pulser tool adjusts said distance between said poppet and orifice to produce a mud pulse signal with a selected pulse height, the mud pulser tool determines a depth at which the mud pulser tool is positioned within the downhole environment, and the selected pulse height is selected based on the depth. 
 
     
     
       2. The mud pulser of  claim 1 , wherein the control system produces a selected pressure drop across the control valve to produce a mud pulse signal with a selected signal-to-noise ratio. 
     
     
       3. The mud pulser tool of  claim 1 , wherein the sensor system further comprises:
 a first pressure sensor operable to measure a pressure upstream of the control valve; and 
 a second pressure sensor operable to measure a pressure downstream of the control valve, wherein the pressure drop across the control valve equals the difference between the upstream pressure measurement and the downstream pressure measurement. 
 
     
     
       4. The mud pulser tool of  claim 3 , wherein the first pressure sensor comprises,
 a first section positioned upstream of the control valve; and 
 a second section positioned downstream of the control valve, wherein the first section and second section are connected by a hydraulic channel. 
 
     
     
       5. The mud pulser tool of  claim 3 , wherein the sensor system comprises an absolute pressure transducer. 
     
     
       6. The mud pulser tool of  claim 3 , wherein the sensor system comprises a differential pressure transducer. 
     
     
       7. The mud pulser tool of  claim 3 , wherein the mud pulser tool
 further comprises 
 a collar; 
 a plurality of threadless modules to be mechanically coupled together into an assembly, wherein the assembly is positioned within the collar; and 
 a retainer operable to couple with the collar and secure the assembly within the collar by compression. 
 
     
     
       8. A system for closed loop control of a mud pulser pressure drop, comprising:
 a mud pump to pump drilling mud into a downhole environment; 
 a mud pulser tool to be positioned within the downhole environment, wherein the mud pulser tool comprises; 
 a control valve comprising an orifice and a poppet actuated linearly relative to said orifice, wherein a distance between said poppet and orifice is adjustable, and the control valve is selectively opened to allow the drilling mud to flow through the mud pulser tool or selectively closed to restrict the drilling mud flow; 
 a sensor system comprising pressure sensors to continuously measure a pressure drop across the control valve while the mud pulser tool is positioned within the downhole environment, wherein the sensor system measures the pressure drop across the control valve when the mud pump is not pumping fluid into the downhole environment to determine a current depth at which the mud pulser tool is positioned within the downhole environment; and 
 a control system to selectively open or close the control valve to adjust the pressure drop to produce a selected pressure drop across the control valve to transmit a selected mud pulse signal through the drilling mud, wherein said distance between said poppet and orifice is adjusted to achieve said selected pressure drop across said control valve, said control system controls said distance between said poppet and orifice to adjust said pressure drop to produce a selected pulse height from said selected mud pulse signal, and the control system determines the selected pulse height based on the current depth; and 
 a surface receiver device to receive the selected mud pulse signal. 
 
     
     
       9. The system of  claim 8 ,
 wherein the sensor system further comprises a survey sensor operable to measure a selected property of the downhole environment; and 
 wherein the survey sensor measures the selected property of the downhole environment at selected depths within the downhole environment. 
 
     
     
       10. The system of  claim 9 ,
 wherein the mud pulser tool comprises a pulser motor assembly to selectively open and close the control valve, wherein the control system is coupled to the pulser motor assembly and selectively controls the pulser motor assembly; 
 wherein the mud pulser tool comprises a power source to provide electrical power to the pulser motor assembly; and 
 wherein the control system restricts the operation of the pulser motor assembly when the mud pump is not pumping drilling mud into the downhole environment to conserve the power source. 
 
     
     
       11. The system of  claim 10 ,
 wherein power source provides electrical power to the sensor system; and 
 wherein the control system is operable to restrict the operation of the sensor system to conserve the power source. 
 
     
     
       12. A method for mud pulse telemetry comprising the steps of:
 positioning a mud pulser tool comprising a flow restriction mechanism into a downhole environment, wherein the flow restriction mechanism comprises a poppet actuated linearly relative to an orifice, wherein a distance between said poppet and orifice is adjustable; 
 circulating fluid through the downhole environment during a first period of time; 
 measuring pressure upstream of a flow restriction mechanism during the first period of time; 
 measuring pressure downstream of the flow restriction mechanism during the first period of time; and 
 obtaining a first differential pressure measurement from the upstream pressure measurement and the downstream pressure measurement; 
 determining a pulse height of the mud pulse signal necessary to allow the mud pulse signal to be received by a surface device from the current depth; and 
 adjusting the configuration of the flow restriction mechanism to achieve a selected differential pressure to produce a selected mud pulse signal comprising the pulse height. 
 
     
     
       13. The method of  claim 12 , further comprising the step of adjusting a configuration of the flow restriction mechanism to achieve a selected differential pressure. 
     
     
       14. The method of  claim 13 , further comprising the steps of
 not pumping fluid into the downhole environment during a second period of time; 
 obtaining a hydrostatic pressure measurement during the second period of time; and 
 estimating a current depth at which the mud pulser tool is positioned in the downhole environment based on the hydrostatic pressure measurement. 
 
     
     
       15. The method of  claim 14 , further comprising the steps of:
 determining a signal to noise ratio of the mud pulse signal necessary to allow the mud pulse signal to be received by a surface device from the current depth; and 
 adjusting the configuration of the flow restriction mechanism to achieve a selected differential pressure to produce a selected mud pulse signal comprising the signal to noise ratio. 
 
     
     
       16. The method of  claim 14 , further comprising the step of limiting energy consumption by the mud pulser tool during the second period of time. 
     
     
       17. The method of  claim 14 , further comprising the step of taking a survey of the downhole environment when the hydrostatic pressure measurement is a selected value. 
     
     
       18. The method of  claim 17 , further comprising the steps of:
 determining a fluid density of the fluid for a selected depth; and 
 determining a fluid flow rate through the flow restriction mechanism based on the fluid density and the first differential pressure measurement. 
 
     
     
       19. A method for mud pulse telemetry comprising the steps of:
 positioning a mud pulser tool comprising a flow restriction mechanism into a downhole environment; 
 circulating fluid through the downhole environment during a first period of time; 
 measuring pressure upstream of a flow restriction mechanism during the first period of time; 
 measuring pressure downstream of the flow restriction mechanism during the first period of time; 
 obtaining a first differential pressure measurement from the upstream pressure measurement and the downstream pressure measurement; 
 adjusting a configuration of the flow restriction mechanism to achieve a selected differential pressure; 
 not pumping fluid into the downhole environment during a second period of time; 
 obtaining a hydrostatic pressure measurement during the second period of time; 
 estimating a current depth at which the mud pulser tool is positioned in the downhole environment based on the hydrostatic pressure measurement; 
 taking a survey of the downhole environment when the hydrostatic pressure measurement is a selected value; 
 determining a fluid density of the fluid for a selected depth; and 
 determining a fluid flow rate through the flow restriction mechanism based on the fluid density and the first differential pressure measurement.